University of Manchester paleontologist Dean Lomax and his colleagues have identified a new genus and species of leptonectid ichthyosaur from a fossilized specimen found in Dorset, England.
Life reconstruction of Xiphodracon goldencapensis. Image credit: Bob Nicholls.
The nearly complete skeleton of a dolphin-sized ichthyosaur was found near Golden Cap in 2001 by Dorset fossil collector Chris Moore.
The specimen includes a skull with enormous eye socket and a long sword-like snout, and represents a new genus and species.
The fossil dates back to the Pliensbachian age of the Early Jurassic, between 193 and 184 million years ago.
“I remember seeing the skeleton for the first time in 2016. Back then, I knew it was unusual, but I did not expect it to play such a pivotal role in helping to fill a gap in our understanding of a complex faunal turnover during the Pliensbachian,” Dr. Lomax said.
“This time is pretty crucial for ichthyosaurs as several families went extinct and new families emerged, yet the new species is something you might call a ‘missing piece of the ichthyosaur puzzle’.”
“It is more closely related to species in the later Early Jurassic, and its discovery helps pinpoint when the faunal turnover occurred, being much earlier than expected.”
“It is the first described genus of an Early Jurassic ichthyosaur described from the region in over 100 years.”
The skeleton and skull of Xiphodracon goldencapensis. Image credit: Dean Lomax.
Named Xiphodracon goldencapensis, the new ichthyosaur would have been about 3 m (10 feet) long and would have dined on fish and squid; the remains even show what may be traces of its last meal.
“This skeleton provides critical information for understanding ichthyosaur evolution, but also contributes to our understanding of what life must have been like in the Jurassic seas of Britain,” said Dr. Erin Maxwell, an ichthyosaur expert at the State Museum of Natural History Stuttgart.
“The limb bones and teeth are malformed in such a way that points to serious injury or disease while the animal was still alive, and the skull appears to have been bitten by a large predator — likely another much larger species of ichthyosaur — giving us a cause of death for this individual.”
“Life in the Mesozoic oceans was a dangerous prospect.”
The authors identified several features in Xiphodracon goldencapensis that have never been observed in any ichthyosaur.
The most peculiar is a strange and unique bone around the nostril — called a lacrimal — that has prong-like bony structures.
“Thousands of complete or nearly complete ichthyosaur skeletons are known from strata before and after the Pliensbachian,” said Professor Judy Massare, an ichthyosaur expert at the State University of NY at Brockport.
“The two faunas are quite distinct, with no species in common, even though the overall ecology is similar.”
“Clearly, a major change in species diversity occurred sometime in the Pliensbachian.”
“Xiphodracon goldencapensis helps to determine when the change occurred, but we still don’t know why.”
The study was published this month in the journal Papers in Palaeontology.
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Dean R. Lomax et al. 2025. A new long and narrow-snouted ichthyosaur illuminates a complex faunal turnover during an undersampled Early Jurassic (Pliensbachian) interval. Papers in Palaeontology 11 (5): e70038; doi: 10.1002/spp2.70038
